Origin story: Khor Kalba

Hopkins Architects’ Simon Fraser on an urchin-inspired turtle sanctuary

The Khor Kalba mangrove reserve in Sharjah is a stunning place, facing out over the Gulf of Oman – you go down to the water and you can see turtles and stingrays, flamingos and collared kingfishers. When we first visited the site for the turtle and wildlife sanctuary in 2016, our client [the Environmental Protected Areas Authority] asked, “where do you want to build?” You feel a sense of responsibility when you do a project like this – you’re putting something down on land that ideally should not be built on.

So we wandered round until we found this old parking lot, strewn with litter and plastic bags, and we thought: we could build on that. Minimising damage to the wilderness site and touching the terrain as lightly as possible were important themes throughout the project. We started with some basic sketches.

The client was still working the programme out as the brief developed, so we needed something we could add to and move around, like drafts on a chequer board. There were piles of broken-up sea urchin exoskeletons all over the place, which have rounded, segmented forms. These gave us the idea for a cluster of seven white concrete pods. They are precast to avoid major building work on site, and sit on simple foundations of in-situ concrete discs, raised above the ground.

At the same time, we were starting work on the Buhais Geology Museum (CQ 273), another environmentally sensitive site 80km away in the Sharjah desert, and we were thinking about designing the projects as a pair. Strangely, we also found fossils of these sea urchins in the middle of the desert, from 65 million years ago, when it was the bottom of seabed. It just reinforced the sense that we should focus on this form.

Externally, the projects look quite different. While the geology museum is clad in metal, Khor Kalba’s pods have a precast concrete shell to protect them from the corrosive saline environment. The shells were cast in segments, like pieces of a pie, and assembled on site. There are three different sizes of pod – 18m, 22m and 30m in diameter, depending on the use, ranging from a cafĂ© and bookshop to a large aquarium – but they all use the same system. Once we had worked out all the details for one section, it worked like a dream.

We did a lot of studies and samples to get the precast elements right. The concrete has a white aggregate with some shell fragments added, and has been sandblasted to give it a rough texture – we wanted that feeling of shells being crushed into it. It was important that it wasn’t too smooth because concrete can appear quite shiny in the strong Arabian light. The precaster did a very good job but, if anything, made it slightly too perfect. I was telling them I wanted more imperfections! 

The scalloping lends definition to the facade from a distance, which is also important in the strong sun. Again, we did a lot of work exploring how the light hit the surface to ensure that the shape was right. Initially we looked at standard rubber moulds, but then realised we could design our own within the budget. We went through a variety of forms – you don’t realise how much work it took to get that fluting. But it looks really sharp.

There’s a lot of sand and silt in the air, and when the wind rises, you get a light run of sand in the dip of the concrete. Beneath the precast cladding is a waterproof membrane and a continuous layer of insulation – these are very well insulated buildings. Visitors step out of the heat and into this sheltered space. It’s naturally lit, but with reflected daylight from the oculus in the centre of the dome. The precast concrete structure is exposed here too, with a grey tone and a fine sandblasted texture, and this helps to regulate the internal temperature.

It’s incredibly hot in the summer months, and can get to 52°C, but the thermal mass definitely has an effect, supplementing the mechanical ventilation. In winter, it’s a more pleasant climate, so at times you can naturally cool the spaces. It’s another aspect of touching the site as lightly as possible. 

Simon Fraser is a principal at Hopkins Architects

Photos Marc Goodwin